A conventional screw pump typically includes an elongated pump casing having a fluid inlet located adjacent a first longitudinal end thereof and a fluid outlet located adjacent a second longitudinal end thereof. A rotatably driven screw (commonly referred to as a “power rotor”) and two or more intermeshing idler rotors extend through the pump casing and operate to drive fluid from the fluid inlet to the fluid outlet. An end of the power rotor nearest the fluid outlet often extends through a ball bearing that supports the power rotor and allows the power rotor to rotate freely about its axis with minimal frictional resistance. The power rotor typically also extends through a mechanical seal that separates the pumped fluid from the ball bearing. This mechanical seal is intended to prevent the pumped fluid from leaking out of the pump and/or from interfering with the operation of the bearing.
A problem commonly associated with screw pumps of the type described above is that the mechanical seal may fail over time, thus allowing quantities of pumped fluid to come into contact with the ball bearing. Since some pumped fluids can be highly volatile and have low flash points, and since ball bearings generally may become very hot (e.g., 200 degrees Fahrenheit) during pump operation, leakage of pumped fluids presents a significant risk of fire and/or explosion. Even in pumps in which ball bearings operate at relatively low temperatures (e.g., in pumps that are operated at relatively low speeds), leaked fluids may wash lubricant out of a ball bearing, thereby resulting in increased friction and heat within the ball bearing which increases the risk of fluid combustion.
Thus, there is a need for an improved seal and bearing design that addresses the above deficiencies in the art.